: The uncommitted output transistors can be configured for either common-emitter or emitter-follower operation, supporting both push-pull and single-ended output modes. Designing with the TL494
If you load the converter circuit past
The TL494 circuit diagram is flexible and robust for PWM control. Key design steps: tl494 circuit diagram
Now that you understand the basics, let's explore how the TL494 is configured for the four most common power conversion tasks. For each application, note how the pin connections—especially the output mode at pin 13—change to suit the topology.
Used for inverters or bridge circuits where two sides need to alternate. Common Applications DC-to-DC Buck Converters : The uncommitted output transistors can be configured
[+12V to +24V Input] | +------+-----------------------+-------------------+ | | | | [C1] [Pin 12: VCC] [Pin 11: C2] [Pin 8: C1] (100uF) | | | | +---[R_T]---(Pin 6) +--------+----------+ [GND] | | +---[C_T]---(Pin 5) | (PWM Output Drive) | v +------+ +-----------+ | | Base (B) | [Pin 14: REF] (5V) | | | | [TIP31] (NPN Power Pass) +---[Resistor Divider]--->(Pin 2) | Collector| | | (C) | [Pin 13: OUTPUT CTRL] +-----+-----+ | | Emitter (E) [GND] | +------+--------+-----> [+5V Out] | | | [D1] [L1] [C2] (1N5822) (100uH) (470uF) | | | | +--[R_F]-+ | | | (Pin 1) Feedback | | [GND] [GND] Detailed Assembly and Design Steps:
| Pin | Name | Function | | --- | ----------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | 1 | 1IN+ | This is typically used for voltage feedback. | | 2 | 1IN- | Inverting Input of Error Amplifier 1. Often connected to a reference voltage or used for feedback. | | 3 | FEEDBACK | Feedback/PWM Comparator Input. This pin is the output of the error amplifier and is connected to the PWM comparator. It is usually connected to an RC network for loop compensation. | | 4 | DTC | Dead-Time Control (DTC) Comparator Input. A voltage applied here (0V to 3.3V) sets a minimum off-time for the output transistors, preventing shoot-through in push-pull and bridge topologies. | | 5 | CT | Timing Capacitor. An external capacitor connected between this pin and ground sets the oscillator frequency along with the resistor on pin 6. | | 6 | RT | Timing Resistor. An external resistor connected between this pin and ground sets the oscillator frequency. | | 7 | GND | Ground. The common ground reference for the IC. | | 8 | C1 | Collector of Output Transistor 1. This is an open-collector output that can be used to drive external transistors in a push-pull or single-ended configuration. | | 9 | E1 | Emitter of Output Transistor 1. Typically connected to ground in common-emitter configurations. | | 10 | E2 | Emitter of Output Transistor 2. Typically connected to ground. | | 11 | C2 | Collector of Output Transistor 2. The second open-collector output. | | 12 | VCC | Positive Power Supply. The IC requires a supply voltage between 7V and 40V. | | 13 | OUTPUT CTRL | Output Control. This pin selects the output configuration. When grounded (logic 0), the IC operates in single-ended mode (both outputs switch in parallel). When connected to REF (logic 1), it operates in push-pull mode (outputs switch alternately). | | 14 | REF | Reference Voltage Output. Provides a stable 5V reference with 5% accuracy, capable of sourcing up to 10mA for external circuits. | | 15 | 2IN- | Inverting Input of Error Amplifier 2. Often used for current limiting or overcurrent protection. | | 16 | 2IN+ | Non-inverting Input of Error Amplifier 2. The second error amplifier’s non-inverting input. | | | 2 | 1IN- | Inverting Input of Error Amplifier 1
Here are some actionable tips to avoid common pitfalls when building your TL494 circuit: